This invention relates in general to a method and apparatus for manufacturing articles, and in particular, to the molding of materials.
More specifically, but without restriction to the particular use which is shown and described, this invention relates to a molded article knock-out method and apparatus to improve the equipment and process for manufacturing articles formed through molding.
Many articles are manufactured by molding them into a desired configuration from a fluent material. One type of molding is known in the art as compression molding by which a blank or "prep" is heated into a fluent state and is compressively caused to assume a predetermined configuration defined by a die cavity. An example of the employment of compression molding as a manufacturing technique exists in the oil seal industry. One common oil and grease seal manufactured by molding comprises a seal body having one or more sealing lips fabricated from a natural or synthetic elastomer, which is bonded to or otherwise cooperates with at least a part of a stiff casing or other structural member. The casing, stamping, or stiffener is utilized to provide rigid mounting of the seal, while the elastomeric seal body in use engages one or more members to provide fluid retention and the like.
It is common practice to manufacture such oil seal articles through the use of the compression molding method because of the relative economy and simplicity of the process. Compression molding permits large numbers of articles to be formed in multiple cavity molds subjected to a single heat cycle of the molding press. It is possible to produce 24, 36, 48 or other large number of parts during one heat cycle of operation of a multiple compressive molding machine. At the conclusion of the molding operation in such apparatus, the plurality of formed products are commonly retained in frictional engagement within components of the machine, such as, for example, cores, sleeves or apertures in one of the molding plates thereof. Such retained molded articles must then be dislodged and removed from frictional engagement for collection of the formed parts and subsequent use of the machine. It is obviously time consuming and highly inefficient to remove such molded articles on a one by one basis, either by hand or machine. Thus, a well known technique of removing molded articles from an immobile position within a plate relies upon simultaneous ejection of all the oil seals by means of a knock-out apparatus, which delivers the articles to an access position for retrieval from the machine.
Typically, such knock-out apparatus include a plurality of plunger-like members, which move into contact with the oil seals and supply a sudden simultaneous impact thereto to physically dislodge each of the articles. The sudden force generated by this simultaneous knock-out technique creates a large impact, which must be compensated for by the use of heavy duty parts in the molding machine. Under the influence of the application of a sudden force to eject the oil seals from the molding plate, the articles themselves are thus subjected to a sudden impact of short stroke, which also must be absorbed by the molding machine. The structure of the molding equipment must be constructed from parts having a suitable strength to resist the knock-out impact and with heavy duty hydraulic systems to apply the required force. The requirement for such stronger and higher output components significantly increases the cost of manufacturing and operating the molding equipment. In addition, the force required to knock-out the molded articles varies, due in part to normal tolerance differences, from seal to seal with the result that the more closely loosely fitting parts require less impact than others. The prior art technique of simultaneous removal fails to take advantage of the varying degrees of retention and applies a single force, regardless of what is required. Thus, the prior art method of knocking-out molded oil seals and the like by a sudden simultaneous jolt requires an elaborate system, which does not attain an optimum level of efficiency and economy.